This invention relates to a scanning type laser emitting device used for treatment of a human nevus.
Human nevi such as birthmarks, moth patches, or freckles are formed by the storage of melanin pigments It is known that the incineration of melanin pigments by a ruby laser light and/or an argon laser light is effective for therapy of these nevi.
However, the laser light generally forms in its energy intensity a Gaussian distribution, and when the laser light produced from a laser generator is applied to the human skin, irregular incineration occurs on the skin, unpreferably reducing the treating effect.
A technique for uniformly forming the energy distribution by propagating the light while repetitively reflecting the light on the surfaces in light transmitting medium in the form of a transparent square bar (hereinafter abbreviated as the "light transmitter") made of acrylic material or optical glass is proposed as a technique for uniformly distributing the output energy of this laser light (Japanese Patent Laid-open No. 27816/1981). In this transmitter, the laser light is incident to the rod-shaped light transmitter and propagated in the transmitter while by a total reflection. Thus, the laser light emitted from the transmitter is uniformly distributed in the energy.
This technique is effective for therapy of the nevi, if a pulse laser light having large instantaneous output like a ruby laser light is used because of its large output density. However, the technique needs a long time to apply predetermined energy to the portion to be cured since the technique produces a small output density in case of using a laser light source capable of outputting only a continuous wave like an argon laser light. Thus, when the treatment is carried out by an argon laser light source, it is necessary to apply laser light for a long period. Therefore, heat is propagated to a range out of the region to be emitted, thereby thermally damaging the healthy tissue of the region not to be treated at the periphery of the nevus. Accordingly, it is not preferable, in view of the treating effect, to use the argon laser light so as to cure the nevus.
Another laser emitting device which produces a laser beam of high output density, though argon laser light, in a uniform energy density distribution is disclosed in Japanese Patent Application No. 203595/1982. In this device, as shown in FIG. 1, light transmitter bundle 2 in which nine prism-shaped light transmitters 4 are, for example, aligned in three rows in three columns is provided Laser beams are sequentially scanned and incident to the incident ends in respective transmitters 4. The laser beams are propagated while being fully reflected individually on the surfaces in the light transmitters, and emitted from the emitting ends after the energy density distribution becomes uniform. Since the section of bundle 2 has a size corresponding to the nevus portion to be cured, the sectional areas of respective transmitters 4 are small. Thus, the energy density (the emitting energy/the sectional area) of the laser beam can be sufficiently high.
In this case, the laser beam is transmitted while being totally reflected in the transmitter. The essential materials capable of transmitting the light and the refractive indexes are:
Quartz glass: 1.4602 (at 5461 .ANG.) PA1 Optical glass: 1.5187 (at 5461 .ANG.) PA1 Ethylene tetrafluoride: 1.35 PA1 Polypropylene: 1.49-1.50 PA1 Air: 1.00
When transmitter 4 is made of quartz glass or optical glass, ethylene tetrafluoride (Teflon: trade mark) or air which has a refractive index lower than that of transmitter 4 should be interposed at the sides (between the transmitters). In other words, the ethylene tetrafluoride is coated, a sheet of ethylene tetrafluoride is arranged on the sides of the transmitters, or air gaps are formed between the transmitters.
However, it is difficult to reduce the coating thickness of the ethylene tetrafluoride to 100 micron or less. Even if the sheet of the ethylene tetrafluoride is interposed between transmitters 4, it is also difficult to reduce the thickness of the sheet to 100 micron or less. Further, even if an air layer is interposed between the transmitters, it is also difficult to reduce the air gap to 100 micron or less. Thus, even if optical transmitter bundle 2 is constructed by bundling rod-shaped light transmitters 4, a light shielding layer having 100 micron or more is presented between the transmitters.
As a result, when a laser light is emitted to a portion to be treated by bundle 2, the portion corresponding to the light shielding layer between transmitters 4 of the portion to be emitted becomes a lattice shade to cause the portion to be emitted to apparently remain. In other words, the lattice-shaped unincinerated remainder occurs on the portion to be cured to be inconvenient in the treating effect.